Question: Solve for $x$ and $y$ using substitution. ${-6x+4y = 2}$ ${y = -x-7}$
Answer: Since $y$ has already been solved for, substitute $-x-7$ for $y$ in the first equation. ${-6x + 4}{(-x-7)}{= 2}$ Simplify and solve for $x$ $-6x-4x - 28 = 2$ $-10x-28 = 2$ $-10x-28{+28} = 2{+28}$ $-10x = 30$ $\dfrac{-10x}{{-10}} = \dfrac{30}{{-10}}$ ${x = -3}$ Now that you know ${x = -3}$ , plug it back into $\thinspace {y = -x-7}\thinspace$ to find $y$ ${y = -}{(-3)}{ - 7}$ $y = 3 - 7$ $y = -4$ You can also plug ${x = -3}$ into $\thinspace {-6x+4y = 2}\thinspace$ and get the same answer for $y$ : ${-6}{(-3)}{ + 4y = 2}$ ${y = -4}$